In the episode is Clay, a jovial and good natured guest at the wedding, he's also humbled by Teds recent career success. He counters this by showing off his pride at being a father...
Also there is Nick, a soon-to-be dad who prentends to be angry at Marshall when he asks how far along his pregnant wife is...
Watchout out for a bridesmaid screaming and running away from Barney!

True to their word, creators Carter Bays and Craig Thomas confirmed that this upcoming season’s first episode takes place at Punchy’s wedding in Cleveland a few days after the finale. But what’s the gang going through exactly? Well, in Lily’s case, she’s finds herself struggling to keep her and Marshall’s big announcement a secret.

“The first episode is the story of: Do you tell people right away or do you wait? How do you keep that secret from the people you care most about in the world?” says Thomas. “So Lily gets there and says, ‘You’re drinking for two tonight. I’m eating for two, so you’re drinking for two.’ And basically, it’s an episode where Marshall gets trashed doing double the shots of everyone.”

For the duo, pregnant Lily has presented a unique challenge in that “one of the biggest questions about Lily getting pregnant was how do we keep Lily at the bar,” says Bays, who himself went through the to-tell-or-not-to-tell dilemma right after his wife became pregnant. “It was a delicate dance,” he joked.

Sarah in Los Angeles, Calif.: I went and sat through Smurfs just for Neil Patrick Harris. I think I deserve some How I Met Your Mother scoop.
You poor thing! We'll try to ease your pain. Those peeps at HIMYM are uber-secretive about the new season, but NPH did reveal this fun little nugget: "I know very little about How I Met Your Mother except I'm in a dance rehearsal all the time. That's all I can talk about. Expect a big dance coming up," he tells us. What's better than Barney rocking some dance moves? No…wait for it..thing!

Question: So excited for the new season of How I Met Your Mother. Are we going to see the fifth and final slap of the slap bet? –Lindsay
Ausiello: Yes… but not necessarily this season. “We will see the last slap,” assures exec producer and co-creator Carter Bays. “The last slap will not be the Russian guy running off into the woods [like] on Sopranos. We will resolve it, but we can’t say whether it’s this year or next year, or the year after that or the year after that, or Season 14.”

Question: Will Lily’s pregnancy span How I Met Your Mother‘s entire season? Meaning, do we have to wait for the finale to see her give birth? —Carolina
Ausiello: Pretty much. The baby arrives during May sweeps. However, we’ll find out if the bundle of joy has a ding-dong or a hoo-hah before then. “There will be an episode before she give birth that’s about what the sex of the baby is,” reveals EP Craig Thomas.

Source: tvline.com

Thanks for the scoop on How I Met Your Mother. Got anything more on Barney and Robin? — Harold
NATALIE: If you liked this, then you'll really love the Barney and Robin dance number! "The premiere is very much about Barney possibly pursuing Nora and Robin wondering how to deal with these feelings she has that are resurfacing for him," executive producer Craig Thomas tells us. "Ultimately, it explodes into this dance number at [Punchy's] wedding that clears the entire dance floor, and they have this big, epic Dancing with the Stars kind of moment, that we're hoping America will want to watch more than DWTS and tune into our show instead." Count us in!

How I Met Your Mother began with Ted (Josh Radnor) being inspired to get his love life together after seeing Marshall (Jason Segel) propose to Lily (Alyson Hannigan). And as the happy couple prepares to welcome a baby in the seventh season, creators Craig Thomas and Carter Bays tell EW Ted’s realization of how little progress he’s made will weigh heavily on him. “He’s thinking, ‘I’m not even where my friends were in the pilot!’” says Thomas. “Well, I don’t think he’s thinking the word ‘pilot,’” Bays finishes with a chuckle.

Joking aside, (and it’s hard to do when you sit down with those two at the same time!) the exec producer duo notes that the trio that is Marshall, Lily, and Ted (who have all known each other since college) will feel a little strain as Ted feels left out of the baby fun. That’s when he takes things into his own hands. “There’s an episode in the first few where Ted really wants to be part of this pregnancy,” teases Thomas. “He wants to be weighing in on decisions and the best diet for Lily. He really wants to be part of it because it’s not happening for him. It’s sort of sweet and cute.”

I need more scoop on How I Met Your Mother. Please oblige! — Edwin
NATALIE: Remember how the producers said this season will solve a lot of past mysteries? Here's another. "There will be a return of another significant Season 1 character," executive producer Craig Thomas tells us. "More significant than the cockamouse," who made a welcome return last season. Hit the comments with your guesses as to who or what is returning!

In the episode is a Benihana chef who appears to be in cahoots with Barney and has made a bet that he can replicate the leading chef’s smooth moves with a knife.
Also featuring is a waitress who tries to have a flirtatious conversation with Marshall but he slams on the brakes with his wedding ring.

Question: Anything new on the How I Met Your Mother front? —Colin
Ausiello: There’s buzz that a major castmember will be full-on streaking in an early episode — or as full on as one can on network television. Jason Segel certainly has experience doing the full monty on camera, but, for my money, this has Barney Stinson written all over it.

Hey, Sandra. These photos from the premiere have me more excited than ever! How about some How I Met Your Mother scoop?! — Abby
I have it on good authority that now is the best time to catch up on the series if you were late to the game. There will be several nods to the mythology this season — and some exciting old favorites returning. You do not want to be left out. With that terribly vague tease, that’s about all I can say for now. Tell me who and what you’d love to see return this season. Time for the last slap? Another visit from Wayne Brady as Barney’s (literal) bro? Sound off and I’ll pass word along. Source: insidetv.ew.com

Question: Can I have a How I Met Your Mother scooplet, please? —Andy
Ausiello: Barney’s going to start lusting after Lily, but there’s a twist: It’s really just her boobs he wants. In the episode the show is currently shooting, Lily’s “pregnancy boobs have arrived,” reveals Jason Segel. “And Barney, being a womanizer, is obsessed with the idea of trying to figure out a way to catch a glimpse of my wife’s new womanly body. Marshall is not happy about it, but he does love a good bet, so he’s into it.” Alyson Hannigan, meanwhile, says the show’s propmaster deserves the credit for Lily’s new curves. “It’s like this major Victoria’s Secret bra, and then there’s little cutlets,” she explains with a chuckle. “I guess there’s going to be a lot of bra stuffing in my future this season.”

How I Met Your Mother, please! Anything will do! — Abel
When Martin Short makes his first appearance this season as Marshall’s new boss at an environmental firm, he warned me earlier this week that we might feel like his part was cut a little, erm, short. He’s only in two scenes — and both are in a swamp. “He’s looking for chemical run-off, but very happy about it — high waders and a big smile on his face,” says Short. But not to worry! When we spoke, he was just a few days away from returning to the set for two more episodes. And these, he said, will reveal that there is much more hiding behind his character’s optimism. Short teases: “We find out there are darker elements to his joy.” How very Damages. Source: ew.com